Modern district heating stations use, to a great extent, biomass as the energy source, the biomass being burnt and the energy released being utilized to heat water to a suitable temperature. To avoid coming under regulatory requirements, for example, for steam boilers or the like, such district heating plants are, as a rule, operated at a temperature not higher than 120° C. and a working pressure of up to 2 bars. In spite of their, in part, large energy production, plants cannot be operated as independent units as they must have electrical energy from an external distribution network for the operation of pumps et cetera.